So far, there is no automatic door hinge able to have a door being opened at a large angle without being moved by the normal flowing air, and no door hinge being furnished with a buffer means; therefore, the door using conventional hinge is liable to be damaged. In the general conventional hinges, once they are installed on the jamb and door, it would be rather difficult to disassemble. Further, the existing general secondary hinges have no satisfactory structure in correcting the deviated axis between the primary and the secondary hinges; as a result, after a long period of use, the door will not be opened or shut smoothly. This invention is particularly designed to improve or eliminate the aforesaid drawbacks of the conventional hinges.